EC6® Enhanced CANDU 6® Technical Summary - Candu Energy Inc.

EC6® Enhanced CANDU 6 ®
Technical Summary

Candu Energy Inc. (Candu) is a leading full-service nuclear
technology company providing nuclear products and
services to customers worldwide.
Our 1,400 highly skilled employees design and deliver
CANDU reactor technology and provide plant life
management, life extension services and regular
maintenance to existing nuclear power stations.
CANDU reactors supply approximately 50% of Ontario’s
electricity and 16% of Canada’s overall electricity
requirements. They are an important component of clean
air energy programs on four continents with over 22,000
megawatts of installed capacity.
Candu Energy Inc. continues to develop products to deliver
2
-free energy with a vision to
the future, while meeting the highest regulatory standards
of the global nuclear industry.
Continuing a tradition of building nuclear reactors for over
for Canada’s nuclear power program and has been adopted
in the nuclear power programs of many countries. The 11
an average lifetime capacity factor of over 87%.
1
34 CANDU reactors in the world, in operation
or being refurbished
4
CANDU reactors can be easily adapted for
2
CANDU reactors consistently rank as top
performers and hold the world record for longest
continuous operation
5
CANDU brand is recognized as one of the top
10 major engineering achievements of the
past century in Canada
3
an average lifetime capacity factor of over 87%

EC6 Evolution 6
Key Passive Safety Features 6
Plant Layout 8
Reactor Building 9
Service Building 9
Turbine Building 9
Unit Output 10
Adaptation to Site Requirements 10
Heat Transport System 12
Steam Generators 13
Heat Transport Pumps 14
Heat Transport Pressure
and Inventory Control System 15
Moderator System 15
Reactor Assembly 16
Reactor Control 17
Fuel Channel Assembly 17
Fuel Handling and Storage System 18
Fuel 19
Emerging Fuel Cycles 20
Safety Systems 21
Shutdown Systems 21
Emergency Core Cooling System 22
Containment System 22
Emergency Heat Removal System 22
Turbine-Generator and Auxiliaries 23
Steam and Feedwater Systems 24
Balance of Plant Services 24
Service Water Systems 24
Heating, Ventilation and Cooling Systems 24
Fire Protection System 24
EC6 Control Centre 26
SMART CANDU® Software Suite 27
Defence-in-Depth and Inherent
Safety Features 30
Severe Accidents 31
Severe Accident Recovery
and Heat Removal System 31
Design Engineering 32
Licensing 32
Project Management 32
Procurement 33
Construction Programs 33
Construction Strategy 33
Plant Performance 34
Features to Enhance
Operating Performance 34
Features that Facilitate Maintenance 35
Modular Air-Cooled Storage (MACSTOR®) 37
Program Details 38
Evolution 39
EC6 Improvements 39
Heat Transport System Key Design Parameters 12
Steam Generator Design Data 13
Heat Transport Pump Data (typical) 14
Total Heavy Water Inventory (per unit) 15
Reactor Core Design Data 16
37-Element Natural Uranium Fuel Bundle
Design Characteristics 19
CANDU 6 Project Performance Record Since 1996 33
Two-Unit Enhanced CANDU 6 Plant 4
CANDU Reactors Worldwide (In operation or
undergoing refurbishment for life extension) 5
Overall Plant Flow Diagram 7
Two-Unit Plant Layout of Major Structures 8
Reactor Building 9
CANDU 6 Units at Qinshan, China 10
Nuclear Systems Schematic 11
Steam Generator 13
Heat Transport Pump and Motor 14
Moderator System Flow Diagram 15
Reactor Assembly 16
CANDU 6 Reactor Face 16
Fuel Channel Assembly 17
Fuelling Machine 18
CANDU Fuel Bundle 19
Flexible Fuel Cycle Options 20
Shutdown Systems 21
Turbine Rotor 23
Latest CANDU 6 Main Control Room 26
SMART CANDU Diagnosis and Action Sequence 27
Barriers for Prevention of Releases 31
Design Engineering and Project Tools 32
CANDU 6 Lifetime Capacity Factors 2011 34
MACSTOR-200 Module at Cernavoda, Romania 37
CANDU Nuclear Power Plant Diagram 40

The Enhanced CANDU 6® (EC6®)
The EC6 is a Generation III, 700 MWe class heavy-water
moderated and cooled pressure tube reactor. Heavy water
(D 2
O) is a natural form of water that is used as a moderator
to slow down the neutrons in the reactor, enabling the use
of natural uranium as fuel. This feature is unique to CANDU
reactors. The choice of D 2
O as the moderator also allows
other fuel cycles to be used in CANDU reactors.
The use of natural uranium fuel in EC6 reactors permits fuel
cycle independence and avoids having to deal with complex
issues such as reprocessing and enrichment. Technology
transfer for localizing fuel manufacture is simple and has
been achieved very successfully in a number of countries.
Natural uranium fuel with on-line fuelling
High localization potential
Suitability for small and medium sized electric grids
Superior safety performance and economics
A proven design based on the highly successful
CANDU 6 reactors
Two-Unit Enhanced CANDU 6 Plant
4 EC6 TECHNICAL SUMMARY

New Brunswick, Canada
Quebec, Canada
Romania
Ontario, Canada
South Korea
China
Argentina
CANDU Reactors Worldwide
(In operation or undergoing refurbishment for life extension)
The EC6 reactor is the evolution of the proven CANDU 6
design. The nuclear steam plant is based on the Qinshan
Phase III CANDU 6 plant in China and is designed to
meet industry and public expectations of nuclear power
generation to be safe, reliable and environmentally friendly.
The EC6 design has been enhanced by using the
experience and feedback gained through the development,
design, construction and operation of 11 CANDU 6
performing well on four continents with over 150 reactoryears
of excellent and safe operation.
While retaining the basic features of the CANDU 6 design,
the EC6 reactor incorporates innovative features and stateof-the-art
technologies that enhance safety, operation
and performance.
The latest Computer-Aided Design and Drafting (CADD)
software tools and innovative integrated systems, linking
material management, documentation, safety analysis
and project execution databases, are used to ensure that
easily maintained by the plant owner.
The EC6 has a target gross electrical output of between
730 MWe and 745 MWe depending on site conditions and
choice of certain equipment. It has a projected annual
lifetime capacity factor of over 92%. This is based on the
that has an average lifetime capacity factor of 87.6%,
ranking CANDU as one of the world’s top performing
nuclear power reactors.
EC6 TECHNICA L SUMMARY
5

EC6 Evolution
The following key enhancements have been introduced
Target design life up to 60 years
Designed for annual lifetime performance factor of
greater than 92%
Design has incorporated feedback from operating
reactors (both CANDU and other designs)
Incorporates modern turbine design, with higher
Increased safety and operating margins
Additional accident resistance and core damage
prevention features
A suite of advanced operational and maintenance
information tools (SMART CANDU®)
Improved plant security and physical protection
Improved plant operability and maintainability
with advanced control room design
Improved severe accident response
Improved containment design features that
provide for aircraft crash resistance, reduced
potential leakages following accidents, and
increased testing capability
These design improvements, along with advances in
project engineering, manufacturing and construction
techniques, result in a reduced capital cost and faster
construction schedule, while enhancing the inherent
safety features of the CANDU design.
Key Passive Safety Features
The EC6 reactor design includes a number of passive safety
features, some of which are design enhancements over the
robust safety systems already existing in CANDU plants.
Two independent passive shutdown systems, each
of which is capable of safely shutting down the reactor
A cool, low-pressure moderator that, in severe accident
situations, serves as a passive heat sink to absorb
decay heat generated by the radioactive fuel channels
A large concrete reactor vault that surrounds the reactor
core in the calandria; the vault contains a large volume
of light water to further slow down or arrest severe core
damage progression by providing a second passive
core heat sink
An elevated water tank located in the upper level of the
Reactor Building that is designed to deliver (gravity fed)
passive make-up cooling water to the moderator vessel
and the calandria vault to remove heat. This delays the
progression of severe accidents and provides additional
time for mitigating actions to be taken.
– Thickened pre-stressed concrete structure designed
to withstand the impact of aircraft crashes
– Leak-tight inner steel liner to reduce potential leakages
following accidents
– Passive spray system from the elevated water tank to
reduce pressure in the Reactor Building in the event of a
severe accident
6 EC6 TECHNICAL SUMMARY

Plant Design
and increased safety. The plant layout provides improved
the use of barriers for safety-related structures, systems
and components that contribute to protection and safety.
Security and physical protection have been enhanced
to meet the latest criteria required in response to potential
malevolent acts.
Overall Plant Flow Diagram
EC6 TECHNICA L SUMMARY
7

Two-Unit Plant Layout of Major Strctures
Plant Layout
The layout for a two-unit plant is designed to achieve the
shortest practical construction schedule while supporting
shorter maintenance durations with longer intervals
between maintenance outages. The buildings are arranged
to minimize interferences during construction, with
allowance for on-site fabrication of module assemblies.
Open-top construction (before placing the roof of the
of installation of equipment and reduces the overall project
schedule risk.
The size of the power block (plant foot print) for a
two-unit integrated EC6 plant is 48,000 square metres.
The power block consists of two Reactor Buildings,
two Service Buildings, two Turbine Buildings, two highpressure
emergency core cooling buildings, two secondary
control areas and one heavy water upgrader building.
A single-unit plant can be easily adapted from the two-unit
8 EC6 TECHNICAL SUMMARY

Reactor Building
The EC6 Reactor Building is a pre-stressed, seismically
compared to previous CANDU 6 designs. Pre-stressed
concrete is reinforced with cables that are tightened to keep
the structure under compression even when the forces it is
designed to withstand would normally result in tension. The
concrete containment structure has an inner steel liner that
The entire structure, including concrete internal structures,
is supported by a reinforced concrete base slab that ensures
a fully enclosed boundary for environmental protection,
biological shielding and aircraft crash protection which in turn
reduces the level of radiation emitted outside the Reactor
Building, during operation, design basis internal and external
events and beyond design basis internal and external events,
Internal shielding allows personnel access during operation
These areas are designed to maintain temperatures that are
suitable for personnel activities. Airlocks are designed as
routine entry/exit doors.
Containment structure perimeter walls are separate from
internal structures, eliminating any interdependence and
Service Building
The EC6 Service Building is a multi-level, reinforced concrete
aircraft crash protected. It accommodates the “umbilicals”
that run between the principal structures, the electrical
systems and the spent fuel bay and associated fuel-handling
facilities. It houses the emergency core cooling pumps and
heat exchangers.
The Service Building also houses the spent fuel bay cooling
Safety and isolation valves of the main steam lines are
aircraft crash protected concrete structure that is located
on top of the Service Building.
Turbine Building
The EC6 Turbine Building is located on one side of the
Service Building wherein the Service Building interfacing
wall is tornado missile and aircraft crash resistant. This is an
optimum location for access to the main control room; the
piping and cable tray run to and from the Service Building;
and the condenser cooling water ducts run to and from the
main pumphouse. Access routes are provided between the
Turbine Building and the Service Building.
The Turbine Building houses the turbine generator. It also
houses the auxiliary systems, the condenser, the condensate
and feedwater systems, the building heating plant, and
any compressed gas required for the balance of plant.
The balance of plant consists of the remaining systems,
components and structures that comprise the complete
power plant that are not included in the nuclear steam plant.
The heat from the reactor coolant converts the feedwater
into steam in the steam generators. The steam from the
steam generators drives the turbine, which in turn drives
the generator to create electricity.
The condenser cools the steam from the steam generator
and converts it back to water (condensate) to be converted
into steam again.
Reactor Building
Blowout panels in the walls and roof of the turbine building
will relieve the internal pressure in the Turbine Building in
the event of a steam line break.
EC6 TECHNICA L SUMMARY
9

CANDU 6 Units at Qinshan, China
Nuclear Power Plant Siting
Unit Output
Each unit of the EC6 two-unit integrated plant design has a
target gross electrical output of between 730 and 745 MWe
depending on site cooling water conditions and the turbine
generators’ technical characteristics.
Adaptation to Site Requirements
The EC6 reactor can accommodate a wide range of
geo-technical characteristics, meteorological conditions
Cooling water systems for all CANDU reactor cooling
requirements can operate at either saltwater or
fresh water sites. The plant can also accommodate
conventional cooling towers. A range of cooling water
temperatures, to suit the plant’s environment, can be
handled. A generic set of reference conditions has been
developed to suit potential sites for the EC6.
The ability to withstand design basis earthquakes at the
plant site. The design basis earthquake is the maximum
ground motion of a potentially severe earthquake that
has a low probability of being exceeded during the life
of the plant. The safety systems are designed to remain
functional both during and after the event.
10 EC6 TECHNICAL SUMMARY

Nuclear Systems
The EC6 nuclear systems are located in the Reactor Building
and the Service Building. These buildings are robust and
shielded for added safety and security. Shielding is a
protective barrier that reduces or eliminates the transfer
of radiation from radioactive materials.
A heat transport system with reactor coolant, four steam
generators, four heat transport pumps, four reactor outlet
is standard on all CANDU 6 reactors.
A heavy water moderator system
A reactor assembly that consists of a calandria installed
in a concrete vault
A fuel handling system that consists of two fuelling
machine heads, each mounted on a fuelling machine
bridge that is supported by columns, which are located
at each end of the reactor
Two independent shutdown systems, emergency core
cooling system, containment system, emergency heat
removal system and associated safety support systems
1
1
3
3
4 4
2
5
5
6
10
10
7
8
9
Nuclear Systems Schematic
EC6 TECHNICA L SUMMARY
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Heat Transport System
The EC6 heat transport system circulates pressurized
heavy water coolant through the reactor fuel channels to
in the reactor core. The heated coolant is circulated through
the steam generators to produce steam that drives the
turbine generator system.
The heat transport system consists of 380 horizontal fuel
channels with associated corrosion-resistant feeders,
four reactor inlet headers, four reactor outlet headers, four
steam generators, four electrically driven heat transport
pumps and interconnecting piping and valves arranged in a
generators and pumps are all located above the reactor.
Heat Transport System Key Design Parameters
Reactor Outlet Header Operating Pressure [MPa (g)]
9.89
Reactor Outlet Header Operating Temperature [°C]
310
Reactor Inlet Header Operating Pressure [MPa (g)]
11.05
Reactor Inlet Header Operating Temperature [°C]
265
Maximum Single-Channel Flow (nominal) [kg/s]
28.5
12 EC6 TECHNICAL SUMMARY

Steam Generators
The EC6 steam generators are similar to those of the
CANDU 6. The tubing is made of Incoloy-800, which is a
material proven in CANDU 6 stations. The light water inside
the steam generators, at a lower pressure than the hot
heavy water reactor coolant, is converted into steam.
Steam wetness, which is the ratio of vapour/liquid
concentration in the steam, has been reduced at the
steam nozzle using the latest steam separator technology,
resulting in improved turbine cycle economics.
Manway
Steam Outlet Nozzle
Secondary Steam Separators
Main Steam Separators
Emergency Heat
Removal System
Shroud Cone
U-Bend
Shroud
Grid Tube Support Plate
Tube Bundle
Tube Bundle Cold Leg
Steam Generator Design Data
Tube Bundle Hot Leg
Number
4
Preheater Section
Shell
Nominal Tube Diameter [mm]
15.9
Main Feedwater Inlet Nozzle
Blowdown Nozzle
Tubesheet
Steam Temperature (nominal) [°C]
260
Coolant Outlet Nozzle
Coolant Inlet Nozzles (2)
Steam Generator
EC6 TECHNICA L SUMMARY
13

Heat Transport Pumps
The EC6 reactor heat transport pumps retain the
CANDU 6 mechanical multi-seal design, which allows for
their easy replacement. The heat transport pumps circulate
reactor coolant through the fuel bundles in the reactor’s
fuel channels and through the steam generators. Electric
motors drive the heat transport pumps.
The cooling of the pump seals lengthens pump service
life and the time that the pump will operate under
accident conditions.
Heat Transport Pump Data (typical)
Number
4
Rated Flow [L/s]
2,228
Motor Rating (MW)
6.7
Heat Transport Pump and Motor
14 EC6 TECHNICAL SUMMARY

Heat Transport Pressure and Inventory Control System
The heat transport pressure and inventory control system
of the EC6 reactor consists of a pressurizer, a degassercondenser,
two heavy water feed pumps, feed and bleed
valves, and a coolant storage tank.
Pressure and reactor coolant inventory control to each
heat transport system loop
Overpressure protection
Heavy water in the pressurizer is heated electrically to
pressurize the vapour space above the heavy water. This
cushions pressure transients without allowing excessively
high or low pressures in the heat transport system.
volume of reactor coolant in the heat transport system that
occurs between zero power and full power. This permits
reactor power to be rapidly increased or decreased,
without placing a severe demand on the reactor coolant
feed and bleed components of the system. Otherwise, the
pressurizer would have to open and close rapidly in order to
compensate for the changing volume of the reactor coolant
in the heat transport system.
When the reactor is at power (normal mode), the pressurizer
controls the pressure in the reactor outlet headers. Electric
heaters add heat to increase pressure, and steam is bled
from the pressurizer to the degasser-condenser to reduce
the pressure. The feed and bleed circuit adjusts the reactor
coolant inventory to maintain the pressurizer level at the
inventory via sprays, to further reduce temperatures and
adjust the reactor coolant inventory before and
after maintenance.
Moderator System
The moderator system of the EC6 reactor is a low-pressure
and low-temperature system. It is independent of the
heat transport system. The moderator system consists of
pumps and heat exchangers that circulate the heavy water
moderator through the calandria and remove the heat that
is generated during reactor operation. The heavy water acts
reactor core.
The moderator slows down neutrons emitted from the
unique to CANDU. It also serves as a backup heat sink for
absorbing the heat from the reactor core in the event of loss
of fuel cooling, i.e. failure of the heat transport system to
mitigate core damage.
An added safety improvement in the EC6 reactor is a
connection to the elevated water tank that provides
additional passive gravity-fed cooling water inventory to
the calandria. This connection extends core cooling and
delays severe accident event progression.
Total Heavy Water Inventory (per unit)
Moderator System [Mg]
274
Heat Transport System [Mg]
198.5
Total [Mg]
472.5
Moderator System Flow Diagram
(Only one loop of the moderator system is shown)
EC6 TECHNICA L SUMMARY
15

Reactor Assembly
The reactor assembly of the EC6 reactor consists of the
horizontal, cylindrical, low-pressure calandria and the
end-shield assembly. This enclosed assembly contains the
heavy water moderator, the 380 fuel channel assemblies
and the reactivity mechanisms. The reactor is supported
is enclosed in the fuel channels that pass through the
calandria and the end-shield assembly. Each fuel channel
permits access for re-fuelling while the reactor is on power.
The ability to replace fuel while on power means there is
minimal excess reactivity in the core at all times, which
is an inherent safety feature. On-power fuelling creates
the prompt removal of defective fuel bundles without
shutting down the reactor. The horizontal fuel channels are
made of zirconium niobium alloy pressurized tubes with
Reactor Core Design Data
Output [MWth]
Coolant
Moderator
Fuel Channels
Lattice Pitch [mm]
2,084
D 2
O
D 2
O
380
286
3
2
7
1
6
5
4
Reactor Assembly
CANDU 6 Reactor Face
16 EC6 TECHNICAL SUMMARY

Reactor Control
The liquid zone control units provide the primary control of
the EC6 reactor. Each liquid zone control assembly consists
of independently adjustable liquid zones that introduce
light water in zirconium alloy tubes into the reactor. Light
water is a stronger absorber of neutrons than heavy water.
Controlling the amount of light water controls the power of
the reactor. On-power refuelling and zone-control actions
provide reactivity control.
The reactor regulating system also includes control
absorber units and adjusters that can be used to absorb
neutrons and reduce reactor power if larger power
reductions are required.
Fuel Channel Assembly
The fuel channel assemblies of the EC6 reactor consist
of zirconium-niobium alloy Zr-2.5wt%Nb pressure tubes,
centred in zirconium alloy calandria tubes. The pressure
each end.
Each pressure tube is thermally insulated from the lowtemperature
moderator by the annulus gas between the
positioned along the length of the pressure tube, maintain
annular space and prevent contact between the two tubes.
fuel channels in opposite directions.
The EC6 reactor is designed for a target life of up to 60
years of reactor operation with provision for life extension
at the reactor’s mid-life by replacement of fuel channels.
Fuel Channel Assembly
EC6 TECHNICA L SUMMARY
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Fuel Handling and Storage System
The fuel handling and storage system of the EC6 reactor
New fuel transfer and storage
Fuel changing
Spent fuel transfer and storage
New fuel transfer and storage involves new fuel being
received and stored in the new fuel storage room in the
operation for at least six months. New fuel is transferred
to the new fuel loading room in the Reactor Building as
required, where the fuel is loaded into one of two new fuel
transfer mechanisms for transfer into one of the fuelling
machines via new fuel ports.
Fresh fuel bundles are inserted at the inlet end of the fuel
channel by one of the fuelling machines. The other fuelling
machine removes irradiated fuel bundles from the outlet
end of the same fuel channel.
The spent fuel transfer and storage handles irradiated fuel
when it is discharged from the fuelling machine and moved
to the underwater spent fuel storage bay. A storage bay
man bridge and handling tools permit safe access and
manipulation of the irradiated fuel and containers.
From the loading of fuel in the new-fuel mechanism to the
discharge of irradiated fuel in the receiving bay, the fuelling
process is automated and remotely controlled from the
station control room.
Fuel changing includes two remotely controlled fuelling
machines, located on opposite sides of the reactor and
mounted on bridges that are supported by columns.
Fuelling Machine
18 EC6 TECHNICAL SUMMARY

Fuel
The EC6 reactor uses the proven 37-element natural
uranium (NU) fuel bundle design. Each fuel element consists
of a column of sintered NU fuel pellets inside a sealed
zirconium alloy tube. The ends of a circular array of 37 fuel
elements are welded to zirconium alloy support plates to
form an integral fuel bundle assembly. Each fuel bundle
is approximately 0.5 metres long and 10 centimetres in
diameter, and weighs about 24 kilograms. Its compact size
and weight facilitates fuel handling. There are no criticality
concerns associated with the handling and transportation
of NU fuel.
The CANDU fuel bundle, with its limited number of
components, is easy to manufacture. All countries
having CANDU reactors manufacture their own fuel. The
manufacture of NU fuel also avoids the production of
enrichment tails. Excellent uranium utilization and a simple
fuel bundle design help to minimize the CANDU fuel cycle
unit energy cost, in absolute terms, relative to other reactor
37-Element Natural Uranium Fuel Bundle Design Characteristics
CANDU Fuel Bundle
Fuel
Natural UO 2
Enrichment Level
0.71wt%U-235
Average Fuel Burnup [MWd/te U]
7500
Bundles per Fuel Channel
12
Fuelling Scheme
8-Bundle Shift
EC6 TECHNICA L SUMMARY
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Emerging Fuel Cycles
The CANDU reactor design is suitable for burning a number
of alternative nuclear fuels. The EC6 reactor retains the
Natural uranium equivalent fuel is produced by mixing
in predetermined proportions of recycled uranium from
commercial light water reactor (LWR) nuclear power plants
(U-235 content ranging from 0.8 to 1%) with depleted
uranium to obtain a blend that is neutronically equivalent
to CANDU NU fuel.
Recovered uranium (RU) (~0.9% enriched) fuel from
reprocessed LWR fuel can be used in CANDU without re-
supply of low enriched uranium fuel at the optimal
enrichment level. The enrichment level is dictated
primarily by the limit placed on fuel discharge burnup.
A thorium cycle or CANDU/Fast Breeder Reactor system.
Long-term energy security can be assured through either
of these. The Fast Breeder reactor would operate as a
material than it consumes.
A high burnup mixed oxide (MOX) fuel that could utilize
plutonium from conventional reprocessing or more
advanced reprocessing options (such as co-processing).
MOX fuel contains plutonium blended with natural
uranium, depleted uranium, or recovered uranium from
reprocessing plant.
for the EC6 reactor. It is three to four times more abundant
than uranium in the earth’s crust and is commercially
reactor, the EC6 reactor is uniquely suited for burning
thorium. A thorium-fuelled EC6 plant would be attractive to
countries with abundant thorium reserves but with little or no
uranium, and can assist in addressing their need for energy
self-reliance.
Thorium Oxide (ThO 2
) also has attractive physical and
temperature is higher than that of UO 2
. As a consequence,
fuel-operating temperatures will be lower than those of UO 2
,
than for UO 2
operating at similar ratings. ThO 2
is chemically
operation, postulated accidents, and in waste management.
Candu Energy Inc. maintains a thorium fuel cycle program
with more than 40 years of history, incorporating reactor
physics and core design; fuel design and fabrication;
irradiation and demonstration; reprocessing; cycle
optimization; and commercial deployment options.
Flexible Fuel Cycle Options
20 EC6 TECHNICAL SUMMARY

Safety Systems
The reactor safety systems are designed to mitigate the
consequences of plant process failures, and to ensure
reactor shutdown, removal of decay heat, and prevention of
radioactive releases. The safety systems in the EC6 design
Independent shutdown systems 1 and 2
An emergency core cooling system (ECC)
A containment system
Emergency heat removal system (EHRS)
The two-shutdown systems, the ECC and the containment
targets with which the system design must comply. This
boundary includes the physical structures designed to
prevent and control the release of radioactive substances.
Shutdown Systems
The EC6 reactor’s two passive, fast acting, fully capable,
diverse shutdown systems are physically and functionally
independent of each other.
Shutdown System 1 consists of mechanical spring-assisted
is based on the proven CANDU 6 design.
Shutdown System 2 injects a concentrated solution of
gadolinium nitrate into the moderator to quickly render the
chain reaction. The gadolinium nitrate solution is dispersed
uniformly throughout the reactor with pressurized gas, thus
Safety support systems are also provided to ensure reliable
electrical power, cooling water and instrument air supplies
to the safety systems. Standby generators are provided as
a backup to the station power for postulated loss of station
power events.
Safety systems and their support services are designed
to perform their safety functions with a high degree of
reliability. This is achieved through the use of stringent
Shutdown Systems
EC6 TECHNICA L SUMMARY
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Emergency Core Cooling System
The ECC system is designed to supply emergency coolant
The high-pressure emergency core cooling system is
designed to provide initial light water injection to the heat
transport system (HTS) from the ECC accumulator tanks
pressurized by air/gas pressure.
Following the termination of high-pressure injection, the
medium-pressure injection system is designed to supply
light water to the HTS from the reserve water tank (RWT)
via the ECC pumps.
Following the termination of medium-pressure emergency
core cooling injection (upon depletion of the RWT),
the long-term automatic ECC injection is provided by
collecting the mixture of heavy water and light water from
the Reactor Building basement and re-circulating into the
HTS via the ECC pumps and heat exchanger.
During normal operation, the ECC system is poised to
detect any loss-of-coolant accident (LOCA) that results in
a depletion of heat transport system inventory (i.e. reactor
coolant) to such an extent that make-up by normal means
is not assured.
The system is capable of maintaining or re-establishing
products from the fuel and maintain fuel channel integrity.
After re-establishing fuel cooling, the system is capable
damage to the fuel.
Containment System
The containment system forms a continuous, pressureretaining
envelope around the reactor core and the heat
transport system. The containment structure protects the
public and environment from all potential internal events,
and is designed to withstand tornadoes, hurricanes,
earthquakes and aircraft crashes; and to prevent the release
of radioactive material to the environment.
The containment boundary consists of a steel-lined,
pre-stressed concrete Reactor Building structure, access
airlocks and a containment isolation system. Local air
coolers remove heat from the containment atmosphere
and are located to best maintain operating containment
pressure and temperature.
A hydrogen control system is designed to prevent the
build-up and uncontrolled burning of hydrogen. It consists
of passive autocatalytic recombiners (PARs), hydrogen
igniters, and a hydrogen monitoring system. In addition, the
containment internal structures are arranged to promote
natural air mixing inside containment.
The provision of a spray system connected to the
elevated reserve water tank will reduce Reactor Building
pressures, if required, in the event of severe accidents.
Emergency Heat Removal System
system that supplies cooling water to the secondary side
of the steam generators, the ECC heat exchangers and the
HTS via the ECC system piping.
The EHRS design ensures that there is an adequate longterm
heat sink available for decay heat removal following
a loss of the normal heat removal systems for the reactor
unit. The EHRS and its supporting structures, systems and
components (SSCs) are designed to operate under the
following postulated initiating events considered as DBAs
Total loss of electrical power (both Class IV and
Class III); or
LOCA followed by site design earthquake after
24 hours; or
Design basis earthquake.
The EHRS is a unitized system. Each unit has two 100%
pumps taking suction from a source of on-site fresh water
that is in a separate location from the main plant service
water system intake.
22 EC6 TECHNICAL SUMMARY

Balance of Plant
The balance of plant comprises the Turbine Building,
steam turbine generator and auxiliaries, condensate
system, condenser and the feedwater heating system with
associated auxiliary and electrical equipment. The balance
of plant also includes the water treatment facilities, auxiliary
steam facilities, condenser cooling water system, and other
systems and equipment to provide all conventional services
to the plant. The cooling water systems could either employ
once-through cooling or a closed loop system utilizing
Turbine-Generator and Auxiliaries
performance and integrity of the nuclear steam plant.
These include requirements for materials (i.e. titanium
condenser tubes and absence of copper alloys in the feed
train), chemistry control, feed train reliability, feedwater
inventory and turbine bypass capability.
reactors are designed to remain at power for the duration of
the event using turbine-generators that are disconnected
from the grid. In this mode of operation, power is only
supplied to internal auxiliaries as needed for the safe
operation of the plant.
The turbine-generator system and the condensate and
by the nuclear steam plant design to ensure optimum
Turbine Rotor
EC6 TECHNICA L SUMMARY
23

Steam and Feedwater Systems
Steam is supplied from the steam generators in the Reactor
Building to the turbine via the steam balance header. The
feedwater system draws hot pressurized feedwater from
the feedwater train in the Turbine Building and discharges
the feedwater into the preheater section of the steam
generators. The feedwater system maintains the required
The condenser steam discharge valves are designed to
condenser, bypassing the turbine. This feature provides for
in conjunction with overall reactor control.
The main steam safety valves provide the safety functions
of overpressure protection and cooling of the secondary
side of the steam generators. The main steam isolation
valves can be used to prevent releases in the event of
steam generator tube leaks to the secondary side of the
steam generator.
Heating, Ventilation and Cooling Systems
Heating, ventilation, air conditioning, and chilled water
(from the chilled water system) are supplied to the nuclear
power plant buildings to ensure a suitable environment for
personnel and equipment during all seasons.
The building heating plant provides the steam and hot
water demands of the entire nuclear power plant HVAC
systems. Steam extracted from the turbine is used as
the steam source for normal building heating. Dedicated,
separate ventilation systems are provided for the main
control area and secondary control area.
Fire Protection System
protection for the entire station, i.e. nuclear steam plant
pumphouse and distribution system is also provided.
Balance of Plant Services
Conventional plant services include water supply, heating,
protection, compressed gases and electric power systems.
Service Water Systems
covering all plant buildings and areas.
The balance of plant service water systems provide cooling
water, demineralized water and domestic water to the nuclear
power plant users. The systems consist of the condenser
cooling water system, raw service water system, water
treatment facility and chlorination systems (if required).
24 EC6 TECHNICAL SUMMARY

Instrumentation and Control
Most automated plant control functions are implemented
in a modern distributed control system (DCS) using a
network of modular, programmable digital controllers that
communicate with one another using reliable, high-security
data transmission methods. The plant is automated to the
level that requires a minimum of operator actions for all
phases of station operation.
The control systems are backed up by the special safety
systems, which include the two independent shutdown
systems, the emergency core cooling system, emergency
heat removal system, and the containment system.
Each of these safety systems operates completely
independent of the other and independent of the reactor
and process control systems. The two shutdown sytems
are independent and diverse from each other (including
fully separate and diverse voting, actuation and shut-down
mechanisms) and each employs triplicated computerized
trip channels. The emergency core cooling, emergency
heat removal and the containment systems also employ
redundant channels and will include at a minimum,
computerized testing and, where appropriate, digital
safety logic.
The I&C design ensures that the random failure of a single
component does not result in the loss of an important
safety or production function. Important functions use
three instrument channels to provide immunity against
single instrument faults. Modular redundancy is used to
provide transparent failover for components such as DCS
controllers, power supplies, and communication modules.
Where enhanced cross-link protection is required, the
same function is redundantly implemented in multiple
independent channels with the outputs from each channel
being supplied to separate voting logic.
EC6 TECHNICA L SUMMARY
25

EC6 Control Centre
The plant control centre makes extensive use of integrated
digital technology to enhance the monitoring and
supervisory control of functions, systems and equipment
necessary for power production, and the monitoring of
functions, systems and equipment important to safety.
The main control room features a main operator console,
with large video display units (VDUs) for plant overview
and annunciation located to the front, and an array of
panels, grouped by major system, located to the sides. The
operator is normally situated at the main operator console
where VDUs provide access to integrated plant information
and controls for normal use. From the console, the operator
has an optimal view of the large overview displays and the
annunciation displays, which together are designed to
improve plant state awareness. From here the operator also
has access to historical data storage and retrieval facilities
to support post event analysis and the monitoring of longer
term trends.
control and monitoring instrumentation is provided on the
control room panels to manage the safety of the reactor and
to prevent damage to costly equipment in the event that the
VDUs normally used are unavailable.
If for any reason the main control room has to be evacuated,
the reactor can be safely shutdown, cooled and maintained
in a safe shutdown state from an independent secondary
control room.
Latest CANDU 6 Main Control Room
26 EC6 TECHNICAL SUMMARY

SMART CANDU® Software Suite
The EC6 comes equipped with the SMART CANDU software
suite which is an integrated package of software tools
and work processes aimed at optimizing CANDU plant
performance throughout its operational life cycle. SMART
CANDU technologies are designed to use the Candu Energy
Inc. knowledge base embedded in predictive models,
to transform discrete bits of plant data into actionable
information used to support operational decisions,
maintenance planning and life cycle management.
The superior engineering SMART CANDU suite of
Intelligent Annunciation Message List System. Assists
operators in coping with events such as blackouts.
Predicts future performance of components, and
determines maintenance requirements and optimal
operating conditions.
components. Ensures optimal margins and maximum
power output.
(MIMC) system. Links health monitor to the plant work
management system.
DATA
ACTION
SMART CANDU Diagnosis and Action Sequence
EC6 TECHNICA L SUMMARY
27

Electrical Power System
The plant electrical power system consists of connections
associated main output system, the on-site standby diesel
generators, the battery power supplies, the uninterruptible
power supplies, and the electrical distribution equipment.
The electrical power distribution systems are separated
into Group 1 and Group 2 in accordance with the two group
separation philosophy. Group 1 system is divided into four
Class I is delivered from batteries
Class II from uninterruptible power supplies
Class III from standby diesel generators
Class IV from the main generator or grid
The emergency power supply (EPS) system is a Group 2
generators are provided for backup power to safety loads
are provided for backup power to some of the safety loads
design basis accident.
28 EC6 TECHNICAL SUMMARY

Nuclear Safety
Nuclear safety requires that the radioactive products from
plant systems for the protection of the plant workforce, and
inside the plant structure for the protection of the public.
product barriers when challenged.
Protection of these physical barriers in each level of
operator actions.
The reliability of the safety functions is achieved by the
structures, systems and components (SSCs) with a high
The use of high-quality components and installations.
Maximizing the use of inherent safety features of the
EC6 reactor.
Providing enhanced features to mitigate and reduce
consequences of design basis events and severe
accidents.
EC6 TECHNICA L SUMMARY
29

Defence-in-Depth and Inherent Safety Features
The EC6 design incorporates four major physical barriers to
the release of radioactive materials from the reactor core to
are contained within the fuel sheath.
The fuel sheath.
are released from the fuel, they are contained within the
HTS. The HTS is designed to withstand the pressures and
temperatures resulting from the accident conditions.
Containment. In the event of an accident, automatic
containment isolation will occur, ensuring that any
subsequent release to the environment does not occur.
Consistent with the overall safety concept of defence-indepth,
the design of the EC6 plant aims to prevent, as far as
practicable, challenges to the integrity of physical barriers,
failure of a barrier when challenged, and failure of a barrier
as a consequence of the failure of another barrier.
During normal operation, the level of defence built in the
design ensures that the plant operates safely and reliably.
This is achieved by incorporating substantial design
margins, adopting high-quality standards and by advanced
reliable control systems to accommodate plant transients
and arrest the progression of the transients once they start.
Following the design basis event, the EC6 safety systems
and equipment automatically start to shutdown the reactor
The design of the safety systems that perform the safety
functions follows the design principles of separation,
diversity and reliability. High degrees of redundancy within
systems are provided to ensure the safety functions can
be carried out assuming a single failure with the systems.
Protection against external events and internal hazards
provided, ensuring independence of systems or components
of postulated events, including severe accidents.
The EC6 design maintains the following traditional CANDU
The low-pressure and low-temperature heavy water
process that is more than an order of magnitude slower
than that of light water reactors. Reactor control and
shutdown are inherently easier to perform.
Refuelling during on-power operation reduces the excess
reactivity level needed for reactor control. Reactor
characteristics are constant and no additional measures,
such as the addition of boron to the reactor coolant (and
its radioactive removal), are required.
Natural circulation capability in the reactor cooling system
can cope with temperature transients (changes) due to
Reactivity control devices cannot be ejected by high
pressure because they are in the low-pressure
moderator and do not penetrate the EC6 reactor
coolant pressure boundary.
Moderator back-up heat sink maintains core coolability
for loss-of-coolant accidents even when combined with
the unavailability of emergency core cooling.
Reserve water tank (RWT) makeup to steam generators by
gravity for station blackout (SBO).
Calandria vault plus shield cooling system or severe
accident recovery and heat removal system (SARHRS)
which could be used to arrest severe core damage
progression within the calandria vessel.
RWT makeup to calandria or calandria vault to delay the
severe core damage progression.
Passive capability of the containment itself, which ensures
emergency response plan is implemented following the
onset of severe core damage.
30 EC6 TECHNICAL SUMMARY

Severe Accidents
In CANDU reactors, fuel resides in fuel channels, which
are surrounded by the cool and low-pressure moderator
inside the calandria vessel, and the cool and low-pressure
shield cooling water inside the reactor vault surrounds the
calandria vessel. A severe accident for CANDU reactors
could only occur when the core cooling by the moderator
system is unavailable.
The CANDU design principle is to prevent severe accident
events and to mitigate them when they occur, minimizing their
Reactivity control
HTS pressure control
Core cooling and the HTS inventory control
Containment heat removal
If severe core damage occurs, the mitigating features
are provided to ensure it will not lead to the failure of the
A large reactor vault water inventory surrounding the
calandria vessel
Using the shield cooling system to remove heat from the
outside surface of the submerged calandria vessel to
the ultimate heat sink via the shield cooling system heat
exchangers or severe accident recovery and heat removal
system (SARHRS)
Defence-in-depth features are provided in the EC6 design
for the extremely unlikely event of calandria vessel failure to
Severe Accident Recovery and Heat Removal System
The SARHRS in the EC6 is provided to prevent and/or
mitigate severe accident progression that may lead to
integrity following a beyond design basis accident. This
system is designed and constructed to deliver cooling
water to the reserve water tank, calandria vessel, calandria
beyond design basis accident.
This system includes gravity-driven, passive water supply
lines and a pump-driven recovery circuit. The reserve water
tank provides gravity-driven water in the short term while
the SARHRS fresh water source is used in the interim prior to
recovery and re-circulation from the Reactor Building sump.
6
2
3
4
1
3
5
7
Barriers for Prevention of Releases
EC6 TECHNICA L SUMMARY
31

CANDU Project Delivery
Through feedback from previous construction projects,
Candu Energy Inc. has been able to optimize key project
elements. The EC6 plant construction schedule, from
The overall schedule, from contract to in-service, is
project dependent but can be as short as 69 months.
The second unit can be in service six months later.
Deployment of the EC6 reactor requires the coordination
and timely delivery of key project elements including
licensing programs; environmental assessments;
design engineering; procurement, construction; and
commissioning start-up programs.
Design Engineering
Preliminary design and development programs of the
EC6 plant are executed in parallel with the environmental
assessment and licensing programs to ensure continuous
and equipment and component maintainability and
constructability requirements are maximized.
The EC6 reactor makes use of the latest computer
from design to construction, and turnover to the plant
owner/operator. State-of-the-art electronic drafting tools
are integrated with material management, wiring and device
design, and other technology applications.
Project Management
The EC6 reactor project management structure
provides fully integrated project management solutions.
Performance management programs are executed from
project concept, through a project readiness mode, to
project closeout.
The project management framework consists of three
decision framework to control each phase of the project
lifecycle; and a comprehensive risk management program.
Licensing
The EC6 reactor builds on the successful CANDU track
jurisdictions in various host countries while retaining the
standard nuclear platform. CANDU 6 has been licensed
in Europe, Asia and North and South America. The EC6
reactor incorporates improvements to meet the latest
regulatory requirements.
Licensing programs are executed and coordinated with
the engineering design programs and environmental
assessment and are structured to support regulatory
process requirements.
Safety & Licensing
Project
Management
Document
Control
ENGINEERING & PROCUREMENT
Design & Analysis
Supply Chain
Management
Performance
Management
Document Control
Supply Chain
Management
CADDS
TRAK
Performance
Management
CONSTRUCTION & COMMISSIONING
Resident Engineering
& Construction
Management
IntEC
CM MS
Hand-Over
Operations &
Maintenance
Project
Management
Document
Control
Supply Chain
Management
Commissioning
Hand-Over
HAND-OVER
Design Engineering and Project Tools
32 EC6 TECHNICAL SUMMARY

Procurement
Construction Strategy
Standardized procurement and supply processes are
implemented to support time, cost, and performance
control (i.e. standardization) and economy in manufacturing
and servicing.
Construction Programs
Constructability programs are implemented to ensure
Maximizing concurrent construction to increase
construction productivity
Minimizing construction rework to decrease
equipment costs
Minimizing unscheduled activities to reduce capital
costs and construction risk
Open-top construction method using a veryheavy-lift
crane
Concurrent construction
Modularization and prefabrication
Use of advanced technologies to minimize interferences
This construction strategy has contributed to the
successful completion of CANDU 6 units around the
world, delivered on budget and on/or ahead of schedule.
CANDU 6 Project Performance Record Since 1996
In-Service
1996
1997
1998
1999
2002
2003
Plant
Cernavoda Unit 1– Romania
Wolsong Unit 2 – South Korea
Wolsong Unit 3 – South Korea
Wolsong Unit 4 – South Korea
Qinshan, Phase III Unit 1 – China
Qinshan, Phase III Unit 2 – China
Status
On Budget*
On Schedule
On Budget
On Schedule
On Budget
On Schedule
On Budget
On Schedule
Under Budget
6 weeks ahead of schedule
Under Budget
4 months ahead of schedule
2007
Cernavoda Unit 2 – Romania
In service Oct. 5, 2007 **
* As per 1991 completion contract
** Work on Cernavoda 2 was suspended in 1989 and resumed in 2003
EC6 TECHNICA L SUMMARY
33

Operations and Maintenance
Plant Performance
The target operating capacity factor for the EC6 reactor
is 92% or more over the operating life of 60 years.
This expectation is based on the proven track record
of CANDU 6 plants, as illustrated below.
Features to Enhance Operating Performance
Incorporation of feedback from utilities operating
reactors (both CANDU and other designs) is an integral
part of the design process. Various new features and
maintenance improvement opportunities have been
incorporated to enhance operating performance
throughout the station life.
Use of improved material and plant chemistry
CANDU plants, e.g. life-limiting components such as
heat transport system feeders and headers have been
enhanced with higher chromium content to limit the
Implementation of advanced computer control and
interaction systems for monitoring, display, diagnostics
and annunciation
Utilization of integrated SMART CANDU suite for
monitoring plant chemistry of systems and components,
and providing predictive maintenance capability
Ensuring capability for return to full power on restoration
of the electrical grid. The EC6 reactor has the capability
to continue operating and delivering house load without
connection to the grid, therefore enabling a rapid return
to full power upon reconnection.
CANDU 6 Lifetime Capacity Factors 2011*
100
80
71.4%
77.1% 80.2% 94.1% 95.2% 95.8%
84.4%
94.0%
89.9% 90.4% 91.2%
60
40
20
0
Point Lepreau
Gentilly -2
Wolsong 1
Wolsong 2
Wolsong 3
Wolsong 4
Embalse
Cernavoda 1
Cernavoda 2
Qinshan III-1
Qinshan III-2
* Source: CANDU Owners Group Inc., “CANDU Station Performance Graphs January–December 2011”, February 07, 2012.
34 EC6 TECHNICAL SUMMARY

Features that Facilitate Maintenance
The number and duration of maintenance outages impact
plant capacity factors. The traditional annual outage
duration has been improved to an average of one month
every 36 months in the EC6 design. To achieve this, the
A maintenance-based design strategy. This program
incorporates lessons learned and ensures maintainability
maintenance program based on SMART CANDU
technology to identify and take mitigating actions, if
required, to ensure plant conditions are diagnosed and
maintained within their design performance limits.
Improved plant maintenance with provisions for
electrical, water and air supplies that are built in for
on-power and normal shutdown maintenance
Shielding in radiologically controlled areas is provided
to minimize worker exposure and occupational dose
Improved equipment selection and system design
outage intervals
EC6 TECHNICA L SUMMARY
35

Radioactive Waste Management
The waste management systems of the EC6 reactor will
and to the public. Radiological exposure for workers
from the plant is monitored and controlled to ensure that
the exposure is within the limits recommended by the
International Commission on Radiological Protection.
The systems for the plant have been proven over many
years at other CANDU sites and provide for the collection,
transfer and storage of all radioactive gases, liquids
and solids, including spent fuel and wastes generated
within the plant.
Gaseous radioactive wastes (gases, vapours or airborne
management system treats radioactive noble gases.
Tritium releases are collected by a vapour recovery
system and stored on-site.
Liquid radioactive wastes are stored in concrete tanks
that are located in the Service Building. Any liquid,
including spills that require removal of radioactivity are
cartridges; compactable solids; and non-compactable
solids. Each type of waste is processed and moved using
specially designed transporting devices if necessary.
After processing, the wastes are collected and prepared
for on-site storage by the utility or for transport to an
In addition, the plant owner/operator maintains an
environmental monitoring program to verify the adequacy
the release point.
36 EC6 TECHNICAL SUMMARY

Modular Air-Cooled Storage (MACSTOR®)
Candu Energy Inc.’s spent fuel dry storage technology
evolved from the concrete canister system, which was
successfully deployed at the Point Lepreau, Canada and
Wolsong 1, South Korea CANDU 6 plants. These concrete
canisters hold up to 540 spent CANDU fuel bundles in nine
baskets, each holding 60 spent fuel bundles for a concrete
canister capacity of approximately 10 MgU. Subsequently,
the MACSTOR-200 storage module was developed to
store 12,000 bundles in 200 baskets and is currently used
to store spent fuel at Gentilly-2 and Cernavoda.
To address larger fuel throughputs of multi unit CANDU
stations, the MACSTOR-200 module capacity has been
doubled, further reducing space requirements and lowering
capital costs. This advanced MACSTOR module design
has been jointly developed with Korea Hydro and Nuclear
storage cylinders instead of two and provides a capacity
of 24,000 bundles stored in 400 baskets. The module is
termed MACSTOR/KN-400 and increases storage density
by a factor of approximately three. Compared to the
MACSTOR-200 module, the Advanced MACSTOR module
requires about 30% less space.
MACSTOR-200 Module at Cernavoda, Romania
EC6 TECHNICA L SUMMARY
37

Technology Transfer and Localization
Candu Energy Inc.’s technology transfer and localization
capable of achieving the highest level of local content in
the shortest time. In South Korea, for example, CANDU
technology achieved up to 75% local content by the
fourth unit. Such accelerated results are possible due
to innovative design, as well as extensive experience
in project management and technology transfer.
With a customer-focused approach, this program
and self-reliance. The resulting partnerships provide
the customer with the “know-why” and “know-how”
EC6 program through a variety of measures, including
equipment standardization and optimization.
Program Details
A successful technology transfer and localization
program is largely dependent upon technical information
as well as personnel development and partnership in
recipient organizations. Candu Energy Inc.’s experience
has shown that success in a technology transfer program
and subsequent localization involves the recognition of
the documentation and implement the technology
technology resides in document form – much of it can
only be transferred through personal communication
program runs concurrently to a nuclear build project,
allowing customers to practice their skills as they learn.
Such an approach prevents knowledge dissipation
and relearning.
of manufacturing techniques, equipment and skills is
often essential
important consideration in any international endeavour
priorities must occur between all parties in order to
minimize overall costs
– Ensure that the necessary infrastructure is in place
to provide adequately trained personnel
– Determine priorities for the areas of technology to
of funds and human resources
– Determine the most suitable recipients who will
receive and eventually develop the technology
– Monitor and coordinate the actual technology
transfer process
38 EC6 TECHNICAL SUMMARY

Summary
Evolution
By capitalizing on the proven features of CANDU
technology, the EC6 reactor has been designed to be
cost-competitive with all other forms of energy,
including other nuclear reactor designs, while achieving
high safety and performance goals consistent with
customer expectations. The size of the EC6 makes it
unique as a product for utilities whose requirements are
for an economic, medium-sized reactor with a proven
performance record.
Heavy water moderator and horizontal fuel channel design
Series of parallel fuel channels – rather than a single
pressure vessel – allowing simpler manufacturing and
reduced costs
Two independent, passive, fast-acting safety
shutdown systems and a unique inherent emergencycooling
capability
minimal excess reactivity burden
Multiple heat removal systems to prevent and mitigate
severe accidents
Very high degree localization
Five decades of excellent operating and safety
performance
EC6 Improvements
The key improvements incorporated in the EC6 reactor
Enhanced safety design, including the addition of a
reserve water system for passive accident mitigation
Upgrades to the emergency heat removal system for
In addition to the robust preventative design provisions to
prevent severe accidents from occurring, complementary
design features are provided to halt the progress and
mitigate the consequences of severe accidents using the
severe accident recovery and heat removal system for
containment heat removal
Optimized chromium content in feeders to reduce
corrosion and enhance life
Steel liner and thicker containment
Improved overall design for maintainability and operability
Competitive economics
Enhanced safety
Improved operability and maintainability
Construction schedule of 57 months achieved by use of
advanced construction methods
Total project schedule as short as 69 months
based on over 150 reactor years of successful operation
by the CANDU 6 reactor
The EC6 reactor will meet customer expectations for safe,
reliable, and economically competitive power production.
technical excellence, and innovations in engineering.
® Registered trademarks of Atomic Energy of Canada Ltd.
(AECL) used under exclusive license by Candu Energy Inc.
EC6 TECHNICA L SUMMARY
39

CANDU Nuclear Power Plant Diagram
1
12
6
9
7
5
3
10
8
4
11
2
Key to Diagram
1 Reactor Building
7
2 Calandria
8
3 Turbine Building
9
4 Turbine generator
10
5 Service Building
11
6 Spray system
12
Pressurizer
Heat transport pumps
Steam generators
Heat transport system
Fuelling machine
Reserve water tank
40 EC6 TECHNICAL SUMMARY

EC6 TECHNICA L SUMMARY
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